Magnetic chuck with fine-mesh faceplate



Oct. 19 1926. 1,603,497

` F. l.. slMMoNs.

MAGNETIC CHUCK WITH FINE MESH FACEPLATE INVENTOR Oct. 19 1926. F. :..slMMoNs MAGNETIC CHUCK WITH FINE MESH FACEPLATE Filed June 25. 1924 5 Sheets-.Swat 2 #MMIII- ATTORNEY Oct. v19 1926.

F. L. SIMMONS MAGNETIC CHUCK WITH FINE MESH FACEPLATE Filed June 25, 51924 5 Sheets-Sheet 3 ATTORNEY Oct. 19,1926.

y F. l, slMMoNs MAGNETIC CHUCK WITH FINE MESH FACEPLATE- 5 Sheets-Sheet 4.

Filed June 25. 1924 lNvEN'goR ,CAMAS-MIA BY WWQRNEY 2 Oct. 19 1926.

.Filed June 19.24v 5 Sheetyshut 5 ATTORNEY Patented Oct. 19, 1926.

fummo STA-Tes 1,603,497 PATENT OFFICE.

shank Lnn'oii 4'siniunirte, orivooirsociinr, nrzonnrsnnnn, Assrcfnon To 'THE Terr; rnncn MANUFACTURING COMPANY, or Woons'oonnr, RHODE ISLAND, A ninfa-` rozenrioiv oF 'nilonn ISLAND.

MAGNETIC entren Wrrn FINE-innen FACEPLATE.

Application `filed June 25, 1924. Serial 10. 722,213.

ilhis invention relates broadly to electrical apparatus and palti'cularly to magnetic chucks. y

The principal vand general object of the invention is to provide a magnetic chuck capable of securely holding a large number ol" small pieces to be operated upon.

Another object of the invention is to provide a magnetic 'chuck having a fine mesh :tace in `which the pole pieces fare of the same width throughout their holding faces and are capable of exerting a high holding force 'for small pieces.

Another object of the invention is to fprovide a magnetic chuck having practically no dead spots even for quite small pieces ot material. V

A -further object olf the invention is to provide chuck ol econoniical and compact cons suction Iand capable ot holding a Alarge nunfiber ot pieces to be Worked on.

An important object ol th'e invention is to provide a magnetic chuck having` 'an auX- iliary detachable face plate adapted to be loaded Awith articles While removed from the chucl'cand 'capable of being livrmly held in place 'on the chuck magnetically and to firmly hold the articles to be operated upon.

Another fand further objecto the invention is to provide "a chuck having Aa detachable 'tace plate which' is li-rmly held in place and functions elliciently even though inaccurately positioned on the chuck.

An impoit-ant object olf the inventionjis to provide a rotary magnetic chuck 'embodying a non-magneticring which acts both Eas a bearing tor the chuck :and as 'a non-magnetic separator' to prevent magnetic flux from passing 'from the `chuck to the frame olI a machine on which it is mounted.

lleiletofore in the art, magnetic chucks have been constructed with the holding laces of the pole pieces of different sizes accordingl to the sizes ol the pieces to be held. lvoivever, the commercial lield for magnetic chucks has been limited to classes oi work in which the pieces to be held have been ol relatively large size due 'to the dilliculties which have been Aencountered when it has been attempted to build a tine mesh77 clinch.y viz, 'one in which the operative tace oi the chuck is finely divided into sections ot ogniosite polarity. In Order to obtain asatisact'ory chuck` having a relatively large operative face, it is necessary to employ a plurality of energizing coils and cores .which kare `operativel upon the face `plate of the chuck at separated points. In the prior `art it has been customary to Wind the coils for adjacent cores in vopposite directions so that adjacent cores `are of opposite magnetic polarity and lines Vor magnetic flux are induced Which pass about a `magnetic circuit comprising a plurality ot cores. In conjunction With cores thus energized, face plates have been provided having` poles Which receive liu'x from a core or cores of positive polarity and transmit it in the direction ol cores 'of negative polarity, From these lace plate poles, the tlur passes to similar Vtace plate poles Which 'conduct the 'iluX 'along `their lengths to cores off negatii'ie polarity. The 'only portion o'i' the flux ivhich is elle'ctive `to hold Work in position is that which is delivered to the very face of the chuck and passes through th'e 'Work after leaving one yset of tace plate pole pieces and before entering the other set. TWith these prior art constructions in which the 'flux is conducted more or less longitudinally along the ,face

- plate pole pieces of 'each set, the flux Wjhic'h is delivered to 'the very tace of the chuck and is available for holdingfarti'cle's -il'n position, is relatively limited and the Aflux density varies 4greatly throughout the Afa'c'e of the chuck. This resultsin sm'afll 4holding Also power andobjectionable 'dead spots. in other 'forms of prior art chucks, the magnetic path is such that an attempt 4to `subdivide the face to fa line mesh results in a greatly diminished and irregular distribution ioff the luX Which is elliectivein holding pieces to be operated upon.

Another disadvantage 'of these prior art cliuclis in which the Aflux passes from 'one core to another is that the length of the flux path is relatively long, thus requiring a large magneto-motive lorce ivith a correspondingly large consumption ol power in order to develop a flux suiiicient for many operating conditions.

r)The present invention disclosed in the tori-n o-t a rotary magnetic chuck overcomes the di'iliculties of the known prior art by construction which there is a disc shaped bose portion ot magnetic material having a plurality of circularly 'disposed upstanding cores. These cores are surrounded collectively by a circular wall upstanding from the base portion at its periphery, and are separated from each other by radially extending partition walls which project upwardly from the base portion and extend from the center of the base portion to the circular wall at the periphery thereof.

The chuck is provided with a face plate' comprising a ring of magnetic material which registers with the circular wall and xwhich surrounds a hub of magnetic material that registers with a corresponding center portion formed at the intersection of the radially extending partition walls. of magnetic material connect the ring with the hub and register with the partition walls which divide the chuck into a plurality of compartments. Extending between adjacent spokes are concentric circumferential portions forming a grid between each pair of adjacentspokes. The construction or the face plate thus far described constitutes what may be termed one of the pole members of the face plate.

Positioned between each pair of adjacent spokes is a flat sector-shaped pole member, which passes beneath the grid of circumferentially extending portions and registers with one of the cores of the chuck. There fiat pole members are provided with-a series of upstanding poles, each in the form of a sector of a ring which projects in a space between, but is magnetically insulated from, a pair o1 circumferentially extending portions connecting adjacent spokes or' the wheel-like pole member olf the race plate.

Each of the cores is provided with an energizing coil and all coils are so wound that the magnetic flux in each of the cores is in the same direction. By means of this construction, the flux passes from each core into the corresponding sector-shaped face plate pole member, from which it is delivered to the face of the chuck by the upstanding poles. From this point the flux passes by way of work-pieces being held on the chuck to the wheel-like pole member comprising the spokes and circumferentially extending portions. and is returned to the bottom oit the cores by wayv of the upstanding circular wall and the partition walls which divide the chuck into compartments.

By means oic this construction a chuck is obtained which has a large and very [ine mesh face, at all points of which there is a relatively high density rlux available vlor holding pieces to be worked on. rlliis particularly adapts the chuck for holding small pieces for multiple surface grinding and j the like.

Each core being in effect, surounded by a shell through whichv the i'lux is returned to the base of the core, a construction is pro- Spokcs vided in which the length of the magnetic path is reduced to a minimum, and hence a minimum magneto-motive force is required to set up a given amount of flux. This efliects a corresponding economy in the power consumed by the energizing coils.

It is realized that the present invention may be embodied in structures other than those disclosed herewith and hence it is desired the present disclosure be considered as illustrative and not in the limiting sense.

Figure l of the drawings is a perspective view showing a rotary magnetic chuck embodying the present invention, with the face plate removed.

Figure 2 is a sectional view partially in elevation taken on the line 2-2 of Figure 8.

Figure 3 is arragmentary sectional view showing the mounting or the slip rings and connection to the energizing coils.

Figure 4 is a plan view or one element of the face plate prior to assembly.

Figure 5 is sectional view taken on the line 5 5 of Figure 4f.

Figure 6 is a plan view of one of the sector shaped pole members of the face plate prior' to assembly.

Figure 7 is a section of the same taken on the line 7-7 of Figure 6.

AFigure 8 is a plan view of the chuck showing the race plate after assembly.

Figure 9 is a fragmentary sectional view taken on the line 9 9 oi4I Figure 8.

Figure l0 is a plan view 0i' the auxiliary face plate.

Figure ll is a sectional view of thesame taken on the line ll-ll of Figure 10.

Figure l2 is a plan view of an alternative form of i'ace plate.

Figure 13 is a plan view of one of the sector shaped pole members of the face plate shown in Figure l2, prior to assembly Figure la is a. sectional view taken on the line lil-14 or' Figure 13. Y

Referring to Figures l and 2, the chuck disclosed comprises a disc-shaped base portion 1,7from which project a plurality of circularly disposed cores 2, which are collectively enclosed by a circular wall 3 upstanding from the periphery of the base portion l. Upstanding from the center of the disc-shaped base portion l is a center portion 4 from which partition walls 5 extend radially to the circular wall 3, thereby dividing the chuck into four compartments, one for each of the core pieces 2. Projecting from the center of the back side of the base portion l is a mounting member 6 by means of which the chuck is adapted to be mounted upon a spindle to be rotated.

Referring to Figures 4 and 5, one element which enters into the construction of the 'face plate or the chuck comprises a ring 10 of magnetic material which surrounds a hub l1 positioned centrally with respect to the massage 13 which are spaced apart forming a grid.

As shown in Figur-es and 9, the portions 13' are, throughout most' of their length, thinner than the ring and hub 11. A,

Referring to Figures 6 and 7, which show one of four sector shaped pole members that enter into the construction oit the face plate, a flat sector shaped piece of magnetic material 2O is provided with plurality of upstandi-ng poles 21, each ot whichI is in the `form of a sector of a ring. The tace plate is assembled by positioning the flat portion of the" sector shaped pole members beneath the grid formed by circumferentially extending portionsY 13, with the poles 21 tittii'a'g in the spaces betiv'een portions 13 of the Wheel-like pole members. These sector shaped pole members are separated irom'the Wheel-like pole member by non-magnetic material such as Babbitt metal 25 shown in Figure. 2. When the face plate has been assembled, the relation between the circumferentially extending portions 13 of the Wheel-like pole member and flat portions O` of the sector shaped pole members is as shown in cross-section in Figure 9'.

The face plate thus assembled is positioned on the chuck body With the ring 1U registering With theupper edge of the Wall 3, the spokes 12 registering With the upper @age of are parution wins 5, the hub n registering with the center portion 4, and thesector-shaped pole members registering with the upper ends of rthe cores 2'. A dou/el 27 aids in centering the Jface plate With respect to the body of the chuck; and the ace plate is held in position by cap screws .23 which pass through the cores 2, the center portion il, and the ivall 3 and are threaded into the magnetic parts of the face plate.

A. gasket 2li; in the Jform of a complete disc, except tor holes for the passage oi' cap screws 28 and doivel 27, provides a watertight seal at the upper edge of circular yvall 3 and lpartition walls 5. A Water-tight lit is made Where insulating Wires traverse the partition Walls 5, and hence the chuck as a Whole is Water-tight, and the vario'us coinpartments are Water-tight with respect to each other. This construction adapts the chuck tor Wet grinding operations; Vand should a leak occur only one coil will be damaged as the fluid Will be confined to a single compartment. 'y Y Aftixed to the underside of the base portion 1 in any suitable manner is a ringshapedbase 30 of insulating material, suoli as a phenol condensation product,I having' molded into it slip rings 31 and Projecting from the plane of the opera-tive faces of the slip rings o1 and 32 is an insulating foi-eign matter;

i bead or ridge* 33, integral with the basse 3i),

which forms a barrier between the rings' 31 and 32, thereby preventing accidental shortcircuiting of the rings, Which might other- Wise be occasioned as by accumulation oit' the slip1 rings 31 to 32 to the energizing Electrical connection from.

coils 33 positioned Within the chuck maybe i in any suitable manner as by such means as stud 34 ig. 3) threaded into tl'ie slipy rings and passing through a bushing 35 in the base portion 1 of the chuck body.

ring 36 of bearingmaterial castin: a)

suitable retaining groove on the underneath side of the base portion 1 provides suitable bearing for rotation of the chuck in service. plementar'y bearing ring (not shown) 'carried by the machine on which the Chuck is mounted.

Ring 36 is made of non-magneticl material and in addition to acting as a bearing' ring, it acts as a non-magnetic separator to prevent magnetic luli'; from passing betiveen the chuck and the body of the chine with which it is used. u

Referring to 'the dotted lines Figure 2f,- it is seen that the flux which passes' to the ring 10 of the face plat-e is returned to the bottoms or" the cores 2 by Way of the' Wall 3 and the portion of the base 1 which :is mediate the Wall 3 and the cores E2. the absence of non-magnetic ring 36,4tl1je reluctance of a pathreprescnted by the dot-dash line 4() through part of `the machine on which the chuck is moi'intedvwould be as louv or lower than the reluctance. of the" path represented by the dotted-,line 41 and hencev a large part of the fl'uX returning from ring 10 to the base of the cores 2 would be operative vto lock the chuck to the grinder or machine on which it is mcmint'ed, thus inter- `lering with its rotation. However, the positioning oi the non-magnetic ring 36 intermediate t-he wall 3 andthe cores Qse'rve to tremendously increase the reluctance ot the path 10, and hence to magnetically insulate the chuck trom the grinder or macl'irine by contining the flux to 'the path 4:1. Y

Referring tothe dotted lines in Figure 2 showing the flux paths, it is seen that the luX is conducted practically perpendicularly to the very face oit the (chuck by the poles 21, from which it passes tlno'i'ig'h pieces such as 61 Which are being held by the chuck, then to portions of the Wheel-like tace plate pole members and is returned lto the `core by a path of minimum length. The Apath of the flux to the very 'lace of the chuck through the poles 21 is 'in nearly all cases in' the direction of the lield set 'up Iby the energizing coils 33 and hence a very high density liuX is delivered to the very fac-e of the chuck and is operative to hold pieces such as 61. The shortness of the total flux y This ring cooperates with a com- Ill f) main face plate.

path reduces the magneton'iotiveforce required to a minimum and hence economizes in the amount of power which the chuck consumes.

The return path ot' that portion ol? the flux which emerges from the tact of the chuck near its periphery is ot especially low reluctance due to the large cross-section of the ring 10 an-d the circular Wall 3. This causes the establishment or'I an especially high holding `torce at the periphery of the chuck, Which is very advantageous in mul-V tiple surface grinding of small parts -for the reason that when the chuck is loaded With parts, those at the periphery are held in place by an unusually strong torce and hence aid in retaining the parts near the center' against centrifugal or grinding forces.

It is seen that the construction is such that the face plate may be subdivided to a very fine mesh Without materially diminishing the density ot the flux delivered to the very face of the chuck and hence that the construction provided is particularly adapted to the holding of very small parts. F urthermore, it is seen that the construction is characterized by very short magnetic paths, thus economizing in the power required to produce a given holding torce.

In the grinding of Very small parts, considerable time is consumed in removing the ground parts from the tace ot the chuck and reloading it With fresh parts, and hence it is desirable to avoid idleness ot' the chuck While this is being done. To this end, applicant provides a plurality of auxiliary tace plates, one of Which is shown in Figures 10 and 1 1. One of these auxiliary face plates is loaded with fresh parts during a preceding grinding operation and When the grinding is terminated, it is interchanged With the tace plate carrying the parts just ground, and operation of the chuck is immediately resumed.

These auxiliary face plates are similar in general construction to the main face plate otl the chuck, and comprise a ring 40 which surrounds a hub 41 magnetically connected to the ring by spokes 42. Extending between adjacent spokes 42 are circumferentially extending portions 43, kforming a grid. The portion thus iar described is a single element magnetically and corresponds to the Wheel-like pole member of the Positioned in the spaces of the grid formed by the circumferentially extending portions 43 are. pieces 44 in the form of a sector of a ring separated magnetically from the remainder ot the tace plate by non-magnetic material 45, such as Babbitt metal or the like. These sector-ota-ring-shaped pieces 44 correspond to the sector-of-a-ring-shape-d poles 21 o'l the main face plate. After one of these auxiliary face .plates have been loaded With small parts,

auxiliary face plate. is adapte-d to cooperate with a depression 47 in the center of the main tace plate, thus aiding in centering the auxiliary face plate. This dowel is preterably removable iirom the auxiliary face plate so that the underside of the tace plate may be reground or retinished Without dihiculty. No dowels are provided for angularV positioning of the auxiliary tace plates for the reason that the chuck is of such fine mesh that there are practically no dead spots, and hence accurate angular positioning ot' the auxiliary tace plates is not necessary.

Figures 12, 13 and 14 show the assembly and one ot the parts for an alternative form ot tace plate for a chuck embodying the present invention. In this form, the face plate comprises a pole member consisting of a ring 50 surrounding a hub 51 and magnetically connected thereto by spokes 52. Projecting from each side of the spokes 52 are circuniterentially extending portions 53. Sector-shaped pole members, such as shown in Figure 13, are provided with circumferentially extending pole pieces 54 Which project upwardly from flat sector-shaped portion 55 and are each in the form of a Seotor of the ring. The center of adjacent poles 54 are connected magnetically by portions 56 upstanding from the flat portion 55. The. tace plate is assembled as shown in Figure 12, With the portion 56 positioned betiveen the spaced ends of circumferentially extending portions 53, the sector shaped pole members being magnetically separated from the Wheel-like pole member by suitable non-magnetic material.

Applicants copending` application, Serial Number 392,951, filed June 30, 1920, discloses a magnetic chuck in which there is a face plate having` a Wheel-like pole member. The structure ot a Wheel-like pole member having a plurality of concentric circumferentially extending portions of magnetic material connected with the spokes of the` Wheel-like structure is claimed broadly in that application.

Having thus described my invention, what I claim is:

1. As an article of manufacture, a face plate for a magnetic chuck, comprising a ring of magnetic material, a plurality of spokes of magnetic material magnetically connected to said ring, a plurality of concentric circumferentially extending magnetic portions magnetically connected to said spokes, and a plurality of sector-shaped pole members having upstanding poles interfitting with said circumterentially extending portions, each of said pole members having on its under side a tlat sector shaped surtace adapted to register with a sector shaped core. j Y

As an article ot manufacture;` a tace plate for a magnetic chuck; comprising a ring ot magnetic material; a hubv ot magnetic material, a plurality of spokes magnectically connecting said ring and said hub; a plurality ot concentric circumterentially extending portions of magnetic material magnetically connected with said spokes; and a plurality ot pole members having upstanding poles interiitting with said circum- :terentially extending portions, each ot said pole members having on its under side a flat sector shaped sur-face adapted to register with a sector shaped core.

3. As an article of manufacture; a pole member `for a magnetic chuck face plate comprising a ring of magnetic material; a hub ot magnetic material positioned concentrically with respect to said ring, said ring being throughout of the same thickness as said hub, a plurality ot spokes magnetically connecting said hub with said ring; and a plurality ot concentric circumferentially extending portions magnetically connecting adjacent spokes.

t. As an article of manufacture; a pole member forthe face plate ot a magnetic chuck comprising a ring of magnetic material; a hub ot magnetic material positioned concentrically with respect to said ring; a plurality of spokes of magnetic material connecting said hub With said ring; and a plurality ot circumterentially extending portions projecting from said spokes, said hub and said ring being of the same thickness and said projecting portions being at least in part of a lesser thickness and having their center portions integral With said spokes.

5. An article of manufacture; a pole member for the face plate ot a magnetic chuck comprising a ring of magnetic material; a hub ot magnetic material positioned concentrically with respect to said ring; a plurality of spokes magnetically connected with said hub and said ring, and a grid formed between adjacent spokes by magnetic members extending from one spoke to another, said ring being throughout ot substantially the same thickness as said hub and the midportions ot the members of said gri-d being of a lesser thickness than said hub.

6. A magnetic chuck comprising a plurality of circularly disosed cores, each ot said cores having an end located in a common plane; an energizing coil embracing each core; magnetic material formed to surround each coil individually With a sectorshaped shell, said shells having edges tern minating in the plane ot said core ends; and a tace plate comprising a pole member registering with the said edges ot each of said sector-shaped shells and a plurality ot additional pole members, one oi which registers With each of said cores. i

7. A magnetic chuck comprising a circulai' base portion, an upstanding magnetic portion projecting trom the center o said base portion, a plurality ot cores circularly"l disposed With respect to said upstanding magnetic portion, an upstanding magnetic Wall surrounding said circularly disposed cores collectively, and a plurality ot radially extending partition Walls magnetically con# necting said upstanding 4portion with said Wall and with said base portion; i-n combi-- nation with a :tace plate comprising a ring ot magnetic material registering With Said circular Wall, a hub ot magnetic material registeringr With said upst-anding portion, and a plurality oi. spokes magneticallyconnecting said hub and said ri-ng and regietering with said adially extending partition Walls.

8. A magnetic chuck comprising la disc shaped base portion, a 'magnetic portion upstanding 'from the center of safd base portion, a plurality ot cores projecting `from said base portion and ci-rcuilarly disposed With respect to said upstanding portion, a circular Wall projecting from the periphery ot said base portion and surrounding said cores, and a wall ot magnetic material between adjacent cores and magnetically connecting said upstanding portion and said circular Wall; in combination with a tace plate comprising a ring of magnetic material registering with said circular Wall, a hub of magnetic material registering with said upstanding portion, a plurality of spokes magnetically connecting said hub and said ring and registering 'with said radially extending walls, a plurality of concentric circumterentially extending portions magnetically connecting ad 'acent spokes, and a pole member positioned between each pair of adjacent spokes and registering With one of said cores, each pole member comprising upstanding poles interiitting with said circumiterentially extending portions.

9. A magnetic chuck comlprising a base portion of magnetic material having a front side and a back side, a protective llange depending from the back side ot the base portion at its edge and integral therewith, a core ot magnetic material projecting from the front side of said base portion, an upstanding magnetic portion projecting trom` the Jiront side ot said base portion and spaced from said core, an energizing coil positioned to set up magnetic `flux in one direction in said core and in the opposite direction in said upstanding magnetic portion,

and a non-magnetic bearing ring on the back side of said base portion adjacent said protective flange and positioned between Said core and said upstanding magnetic portion to prevent magnetic flux :trom passing hetween the protective flange and the core by way ot the machine on which the chuck may be mounted.

l0. A magnetic chuck comprisiirqw a base portion ol magnetic material having a front side and a back side, a protective A[lange depending from the back side of the ybase portion at its edge and integral therewith, a wall of magnetic material projecting from the front side ot said base portion at its edge, a core ot magnetic material projecting from the front side of said bare portion, an energizing coil positioned to set up magnetic flux in one direction in said core and in the opposite direction in said wall, and a nonmagnetic bearing ring on the back side of said base portion adjacent said protective flange and positioned between said core and said wall to prevent magnetic flux from passing from said wall to said core by way of parts ot a support on which the chuck is mounted.

ll. A magnetic chuck comprising a disc shaped base portion of magnetic material having a front side and a back side, a protective flange depending from the back side of the base portion at itsl edge and integral therewith, a wall of magnetic material projecting from the front side of said base portion at its periphery, a plurality of circularly disposed cores of magnetic material projecting from the front side of said base portion, means to induce magnetic flux in one direction in each core and,` in the opposite direction in the corresponding portion of said wall, and a bearing ring of nonmagnetic material positioned on the back side of said base portion adjacent said protectiie flange and positioned between said wall and Said cores to prevent magnetic flux from passing between the protective'llange and the cores by way o1c the machine on which the chuck may be mounted.

l2. As an article of manufacture; a pole member for the tace plate of a magnetic chuck comprising a rim ol magnetic material; a magnetic portion positioned within said rim, said rim, being throughout of substantially the same thickness as said magnetic portion; a plurality of bars magnetically connecting said rim with the magnetic portion positioned within the rim; and a grid formed between adjacent bars by magnetic members extending from one bar to another.

FRANK LEROY SIMMONS. 

